Process for the production of zinc metal



ug- 3, 1954 P. L. sCHEREscHEwsKY 2,635,506

PROCESS FOR THE PRODUCTION OF ZINC METAL Filed June 20, 1951 Patented Aug. 3, 1954 UNITED PATENT PROCESS EUR THE PRODUCTION F ZINC METAL 9 Claims.

The present invention relates to a process` for the production oi zincmetai,

More particularly the presentinvention relates to a process for obtaining purezinc froma zinc ore or zincfhearing material wherein. the zinc is largely in the form of zinc oxide.

Although it has previously been proposed to treat zinc bearing materials with reducing eases or, in the alternative, by reducing the molten zinc bearing material with a layer of coke at the surface, in general these prior processes have been characterized by relatively low yield and in some instances by the productionof zinc oxide rather than zinc.

The present invention relates-to a novel process for the direct production of zinc metal by the reduction of zinc oxide and the volatilization of the zinc thus produced in arapid and economical manner.

It has further been discovered inaccordance with the present invention that by blowing a zinc-containing molten medium having a high zinc content, i. e. more than 18%, with a stream of substantially pure carbon monoxide, the molten zinc medium being provided with a thick layer of coke granules on the surface thereof and a copper mattebelow the medium, a highly eiicient process for the continuous reduction and production of Zinc metal'was effected;

In accordance with the present invention a conventional water-,jacket zinc-filming furnace ischarged'with a molten zinc-.bearing medium capable of remaining iiuid at atemperature between 1200D and l500 C. while bearing a large proportion of zinc in the form of zinc oxide, as for, example from 18 to as high as 35% ofrzinc, preferably between 2()v andr 25%. In addition to the zincfbearing material-the furnace is also charged with a copper matte, i. e. largely consisting of copper sulphide, which forms thebottorn layer and will be effective to concentrate the lead, copper, nickel and silver of the zinc ore being charged to the furnace.

The present invention may be better understood by. a reference tothe gures of the drawing wherein:

Flg- 1 iS a diagrammatic flow sheet illustrating the process of the. present invention; and

Fig, 2-is .a diagrammatic .detail of a modied heating arrangement for the furnace.

Referring tothe figures of the drawing, a conventional type VA0f Water-cooled'furnace isinE dicated diagrammatioally at I0. The furnace is provided with a layer of high zincfcontaining slag II4 and a bottomlayer of copper matte IZ.

In Starting the furnace preferably the bien zinc- Centainine Slag is. molten in separate crucible and charged into the furnace. Thereaiter-thecone permette is added to the suriace .of the slag and beine of a high Speelde gravity falls to the bottom while mixing intimately. with the. Slag and picking un lead, silver orironor excess iron impurities. Thereaiter a layer' of granulated coke is added to the slag, this layer of coke-being relatively thick, i. e. six inches or more, and indicated at I3. The slag isv preferably initially heated to a temperature between 1290i and 1500- C- AS Shown by the arrow I4, the furnace is Continuously heated as needed by blowing the same with a mixture of powdered carbon` and oxygen. The slagV layer isalse blown, as indi- Gated by the arlOW l5., with a mixture ofk carbon monoxide and powdered zinc. oxide ore. in order to insure proper reduction theslaer layer s further blowny as indicated by the arrow IG, with carbon monoxide carrying in suspension pow,-V dered Carbon Finally, the matte layer is blown inter-1nittentlvl with small quantities of carbon monoxide asiidicated by thearrow. I1 in order to insure turbulence and mixing off the matte with the slag.

Bassing from theupper endLofthe furnace It, as indicated by the arrow I8, isthe volatilized zinc and carbon-- monoxide which is produced in accordance with the following equations:

The carbon monoxide gas carrying the volatilized zinc is led to-a suitable condenser, such as the well-known WbeatonfNaiarian condenser, indicated at I9, wherein the gas is cooled to a tem.- perature of approximately 500 C. and'liquid'zinc is produced as indicated by the arrow 2o. The carbon monoxide separated in the condenser,- as indicated by the arrow 2l, goes through a blower 22 andthe major portion thereof passes through a` regenerative heater 23, asindicated by the ,arrow 24, 1li the, regenerative heater a portion of the. carboninonoxide is burned with air, as indicated by the arrows zandli, to pro: duce heat andto heat the major portion of the carbon monoxide to approximately 10Go? C. so that when it is charged into the furnace the carbon monoxide will be at a relative high temperature and will not tend to cause solidication thereof. The vturbulence inthe furnace and the slag layer thereof, particularly causedby the in? jection of the relatively hot carbon monoxide,

will cause contact between the slag and the relatively thick layer of coke i3 so that any unreduced zinc oxide will tend to be quickly reduced to zinc and volatilized.

The zinc-bearing medium, or slag, is preferably a basic iron-zinc silicate having the formula SiO2.FeO.ZnO which is capable of retaining its molten, iiuid form although containing a high percentage of zinc. This material may be prepared by fusing together iron oxide, silica or silica and lime in order to produce a magma.. melting at a temperature of approximately 1200 C'. Thereafter zinc oxide may be added thereto to produce a melt which may contain as high as approximately 35% of Zinc and as low as 10% of silica together with a small quantity of lime, the balance being principally ferrous oxide. Preferably, however, a lesser quantity of Zn oxide is added in forming the slag so that the molten slag will be capable of quickly dissolving zinc oxide as added thereto. In addition to blowing the slag with carbon monoxide bearing powdered zinc oxide ore, or in suspension therein as previously pointed out, the molten magma is also blown with carbon monoxide carrying powdered carbon which produces the initial reduction within the body of the slag, further reduction taking place. as heretofore set forth, in the coke layer through which the molten fluid mass is admixed because of the high degree of turbulence. The additional heat necessary may be supplied to the furnace by injecting powdered carbon and oxygen, as indicated at I4, the burning of the carbon and oxygen to carbon monoxide supplying additional heat. Of course if any of the carbon is burned to carbon dioxide this carbon dioxide will be reduced by the excess carbon or by the coke layer so that the output from the furnace is always carbon monoxide and zinc metal, no zinc oxide being volatilized. From time to time some of the zinc-bearing material may be tapped off through the tap indicated diagrammaticaliy at 2l and further quantities of slag components added to the bath to maintain the composition of the molten slag mass. Similarly at rare inten vals a tap indicated diagrammatically at is utilized to remove a portion of the matte and matte components may also be added, i. e. copper sulphide. In addition to or in place of burning a portion of the carbon monoxide in the regenerative heater a portion of the carbon monoxide may be taken off through the lead indicated at 2S to a gas turbine indicated at 30 which can drive an A. C. generator, the leads from the enerator being indicated diagrammatically at 3l. Here again the electricity generated may be utilized to heat the furnace l0 in a conventional manner so as to aid in maintaining the necessary temperature.

Still another method for heating the bath is "i Example I Into a conventional water-jacketed furnace of approximately 8 x 15', suicient slag is poured to furnish a layer a foot to a foot and a half in depth at a temperature of 1200 to l300 C. This slag may be prepared by melting in a cru-cible or other heating vessel by fusing together iron oxide, silica and a small quantity of lime and thereafter adding zinc oxide so that a molten mass is produced containing 20% of zinc oxide, 10% of silica, a small quantity of lime and the balance iron oxide. Thereafter to the molten slag in the furnace is added sumcient copper matte in liquid form to form a matte layer at the bottom of the furnace of approximately six inches in depth. Finally to the furnace is added sufcient coke of a granular size of from one-fourth to one inch to form a layer of six inches or more on the surface of the liquid slag. Thereafter the furnace is blown with approximately four pounds of carbon monoxide per minute per square foot of bath surface. Part of the carbon monoxide is formed by feeding the furnace with a stream of 98 oxygen, i. e. substantially commercially pure oxygen, carrying powdered carbon to furnish sufficient heat to maintain the temperature of the bath at approximately l300 C., or from 1200 to 1500" C. To one of the carbon monoxide streams entering the furnace is added additional powdered zinc oxide ore in order to maintain the composition of the bath, and to another carbon monoxide stream entering the bath there is added an excess of carbon. Approximately three additional pounds of carbon monoxide per minute per square foot will be formed as a result of the various reactions so that the final output of gas containing the volatilized zinc will be of the order of seven pounds of carbon monoxide per minute per square foot of furnace surface containing approximately three pounds of zinc per minute per square foot of furnace surface. The additional carbon monoxide generated, i. e. the three pounds of carbon monoxide, need not be recycled through the bath and is preferably burned in the preheater 23 to heat the carbon monoxide coming from the condenser through the line 2l from a temperature of 500 to a temperature of l000 C. Preferably the carbon monoxide fed into the furnace is fed through suitable tuyres and at a sufiicient rate so as to agitate both the bath and at least a portion of the carbonaceous granular layer above the bath so that the granular coke or other carbonaceous reducing agent will enter into the reaction. Because of this violent agitation a relatively thick layer of coke or other carbonaceous reducing agent may be utilized since the reaction will taire place substantially through the entire layer. From time to time additional coke granules may be added to the surface of the bath so as to maintain a layer in excess of six inches thick. The stream of carbon monoxide fed into the matte layer will also result in agitating the same and greatly increase the ability of the matte layer to extract silver and other metals from the zinc oxide ore being fed continuously into the furnace.

I claim:

l. A continuous process for the production of j zinc metal from zinc oxide ore which comprises continuously feeding the ore into a molten bath of a zinc-bearing medium capable of remaining fluid at temperatures of between 1200 and 1500o C. while having a zinc content greater than 18% and having a layer of granular carbonaceous reducing agent on the surface thereof, passing into Said bath a high velocity stream of carbon monoxide gas having suspended therein powdered carbon to agitate both said bath and carbonaceous layer and mix the moltenbath with the layer,

so as to reduce said zinc oxide ore to zinc metal and produce carbon monoxide, heating said bath to volatilize said zinc metal, condensing said zinc metal and separating the same from the vcarbon monoxide gas, and recycling at least a part of said carbon monoxide to the molten bath.

2. The process of claim 1 wherein a portion of the carbon monoxide gas produced during the reaction is burned to produce heat which is utilized for heating said bath.

3. The process of claim 1 wherein a portion of the carbon monoxide gas produced is burned and the heat of combustion is utilized to heat the carbon monoxide gas recycled to the bath.

4. The process of claim 1 wherein the bath is heated by the combustion of powdered carbon and oxygen injected thereinto.

5. A continuous process for the production of zinc metal from zinc oxide ore which comprises continuously feeding the ore into a molten bath of a zinc-bearing medium capable of remaining fluid at temperatures of between 1200 and 1500 C. while having a zinc content greater than 18%, a layer of granular carbonaceous reducing agent on the surface thereof and a layer of copper matte below said bath, passing into said bath a high velocity stream of carbon monoxide gas having suspended therein powdered carbon to agitate both said bath and carbonaceous layer and mix the molten bath with the layer, so as to reduce said zinc oxide ore to zinc metal and produce carbon monoxide, and passing into said matte layer a second stream of carbon monoxide gas to admix said matte with said bath 4and thereby extract metals other than zinc from said ore, heating said bath to volatilize said zinc metal, condensing said zinc metal and separating the same from the carbon monoxide gas and recycling said carbon monoxide to the molten bath,

.6. The process of claim 1 wherein the layer 0I granular carbonaceous reducing agent is greater than six inches in thickness.

7. The process of claim 5 wherein the layer of granular carbonaceous reducing agent is greater than six inches in thickness.

`8. The process of claim 1 wherein the molten l bath is a basic iron-zinc silicate.

9. The process of claim 5 wherein the molten bath is a basic iron-zinc silicate.

` References Cited in the file of this patent UNITED STATES PATENTS Number Name Date 701,458 Armstrong June 3, 1902 2,144,942 Seguine, Jr. Jan. 24, 1939 2,473,611 Robson June 21, 1949 2,475,607 Garbo July 12, 1949 2,493,823 Morrison Jan. 10, 1950 2,598,743 Waring et a1 Jan. 3, 1952 

1. A CONTINUOUS PROCESS FOR THE PRODUCTION OF ZINC METAL FROM ZINC OXIDE ORE WHICH COMPRISES CONTINUOUSLY FEEDING THE ORE INTO A MOLTEN BATH OF A ZINC-BEARING MEDIUM CAPABLE OF REMAINING FLUID AT TEMPERATURES OF BETWEEN 1200 AND 1500* C. WHILE HAVING A ZINC CONTENT GREATER THAN 18% AND HAVING A LAYER OF GRANULAR CARBONACEOUS REDUCING AGEN ON THE SURFACE THEREOF, PASSING INTO SAID BATH A HIGH VELOCITY STREAM OF CARBON MONOXIDE GAS HAVING SUSPENDED THEREIN POWDERED CARBON TO AGITATE BOTH SAID BATH AND CARBONACEOUS LAYER AND MIX THE MOLTEN BATH WITH THE LAYER, SO AS TO REDUCE SAID ZINC OXIDE ORE TO ZINC METAL AND PRODUCE CARBON MONOXIDE, HEATING SAID BATH TO VOLATILIZE SAID ZINC METAL, CONDENSING SAID ZINC METAL AND SEPARATING THE SAME FROM THE CARBON MONOXIDE GAS, AND RECYCLING AT LEAST A PART OF SAID CARBON MONOXIDE TO THE MOLTEN BATH. 